1. Field of the Invention
The present invention relates to pulpers for a fiber suspension, and, more particularly, to pulpers having an extraction plate for separating good fibers from effluent.
2. Description of the Related Art
A pulper is used for making fibers which are used in a fiber suspension in a paper-making machine. The source of fiber may be, e.g., wood fiber in the form of virgin fiber or recycled fiber. The pulper grinds the source of fiber into individual fibers which are used in the fiber suspension in a paper-making machine.
It is known to use a pulper with a screen plate and a rotor which are disposed within a vessel. The rotor causes the source of fiber to rotate past the screen plate. Good fiber passes through a plurality of holes in the screen plate for further processing, while undesirable substances such as foreign matter, etc., do not pass through the holes in a screen plate and may be discarded.
It is also known to provide a screen plate with inserts which are respectively disposed within corresponding holes in a screen plate. The inserts are irremovably attached to the screen plate, such as by arc welding. The inserts may become worn over time. To replace the inserts, the screen plate must be removed from the pulper and the inserts are ground off flush with the screen plate. Additionally, it is often necessary to drill out. the inserts after the grinding operation since the penetration depth of the weld also extends into the screen plate. For these reasons, it is very difficult to replace the inserts in a conventional screen plate. In fact, it is often times less expensive to simply scrap and replace the screen plate.
What is needed in the art is a screen plate which may be easily repaired when the inserts become worn through use.
The present invention provides a pulper with an extraction plate assembly with a plurality of inserts which are removably attached to a wear plate.
The invention comprises, in one form thereof, a pulper for pulping a fiber suspension, including a vessel, an extraction plate assembly and a rotor. The extraction plate assembly is disposed within the vessel and includes a metal plate with a plurality of holes extending therethrough. A plurality of metal inserts are respectively disposed within the holes and project from the plate. Each insert is removably attached to the plate. A rotor is disposed within the vessel adjacent to the extraction plate assembly. The inserts are removably attached to the plate by brazing the inserts within the holes, or slightly shrinking the inserts using liquid nitrogen and placing the inserts in the holes.
An advantage of the present invention is that the inserts can be replaced without removing the extraction plate assembly and without disassembling the entire pulper.
Another advantage is that the inserts can be relatively easily changed from one shape to another, depending upon the specific application.